Ontario Field Crop Report
May 7, 2008
by OMAFRA Field Crop Specialists
For emerging issues, questions or to provide feedback on this report, contact the CropLine at 1-888-449-0937. Technical information can also be obtained at the OMAFRA Field Crops Webpage at www.ontario.ca/crops and Crop Pest Ontario at www.omafra.gov.on.ca/croppest/. Referenced OMAFRA Publications include Publication 811 Agronomy Guide for Field Crops ($20), 812 Field Crop Protection Guide ($15), 75 Guide to Weed Control ($15), and 505 Ontario Weeds ($15). These can be obtained from your OMAFRA Resource Centre, or by calling 1-800-668-9938.
Forage
Alfalfa development has stalled during the cool conditions of the first week of May, after growing vigorously in the last part of April. Grasses have been catching up to the alfalfa with the arrival of cool, wet weather.
Winter annual weeds are evident in new alfalfa seedings as they bolt to flower. Control is generally not warranted since they will not regrow after the first cutting, but if pressure is high, it should be noted for control during the next phase in the crop rotation.
Nitrogen can dramatically increase the yield of grass stands. Good grass stands with less than one-third legume, can benefit from 50 to 100 lbs/acre of nitrogen. Optimum rates depend on the cost of nitrogen, anticipated value of the hay, thickness of stand, moisture conditions, and whether it is pasture or hay. The first application of nitrogen for hay should have been made as early as possible in the spring at green-up. Additional applications can be made after each harvest or grazing rotation.
Pasture
Early growth of pastures has generally been excellent, and livestock are appearing on grass as quickly as the fences are fixed. The difference in early growth between well-managed and over-grazed pastures is astounding.
In a continuous grazing system, pastures should be 15 to 25 cm (6 - 10 inches) before turnout, depending on grass species and stocking rate. In a rotational grazing system, livestock can begin grazing earlier, at 8 to 10 cm (3 - 4 inches), but should be moved through the first rotation very quickly in order to keep up with the rapid spring growth. The most efficient forage height for a cow to graze is from 10 to 25 cm (4 - 10 inches) and 8 to 15 cm (3 - 6 inches) for sheep and horses.
Changing from a continuous grazing system to rotational grazing by subdividing fields and moving livestock, can double the forage production and reduce the amount of hay required during a dry summer slump. The more paddocks in a rotational system, the better the results. Forage rest (regrowth) periods should be about 30 days between rotations, depending on growing conditions. Ideally, daily moves to a fresh pasture with a 30 paddock system will optimize forage growth and livestock production. A 6-7 paddock system with moves every 4-5 days will provide the 30 day rest period and works well. Even a less intensive 4 paddock, 10 days grazing, 30 day rest system can increase production over continuous grazing.
Corn
Corn planting is progressing rapidly. Emergence has mostly occurred on the early-planted corn and stands generally look good. Some plants are pale green because of the weather stress, but should come along quickly with some heat.
There was some injury to emerged or close-to-emerged corn when frost occurred on April 29-30. In some locations, temperatures recorded at ground level were -10°C. Mild injury included the tips of the emerging leaf being “nipped off”. More severe injury included freezing injury to the seed, killing the plant because the freezing temperatures occurred at the growing point. These fields should be checked for stand and plant vigour. It is interesting to note that radicals (first roots) can be burned off by fertilizer burn in the seed furrow and recover, but young coleoptiles (first leaf) that receive these killing temperatures down into the soil do not recover.
It usually takes 6 to 21 days for corn plants to emerge. Approximately 180 corn heat units (CHU) are required for this to occur. At present temperatures (May 7th), heat unit accumulation has been less than 10 CHU per day.
When looking at the long term forecast for the remainder of May, a fair number of rainy days are predicted. If this occurs, it may be beneficial to move onto the land with a shallow, fast, light tillage to dry out and warm up the ground in preparation for planting. Compaction resulting from getting on the land too early is a concern. Tractor and equipment tire pressures should not exceed 15 psi in order to prevent compaction.
If planting is delayed and you are thinking about switching to lower CHU hybrids, consider that this usually does not need to be done until May 20th. However, if you were overly aggressive with picking your early hybrids (200 CHU or more than your area) and planting has been delayed, consider switching back to normal length hybrids now.
In Roundup Ready corn, consider weed control programs that apply low rates of pre-emergence herbicides that will extend the window for applying your full postemergence program. Depending on the activating moisture conditions under which the early pre-ermergence are applied, they can provide extended periods of weed control and ensure that later emerging weeds are more uniform in size and stage to optimize timing of the postemergence programs.
Soybeans
Cold and wet conditions have delayed early planting of soybeans. Soybean seed needs to be handled with extra care due to harvest conditions last fall that adversely affected seed quality. Seed harvested last fall is low in moisture and has a thin seed coat. Mechanical damage to seed from handling can damage or injure the embryo which is located near the surface of the seed. Soybean seed treatments will not improve germination of mechanically damaged seed. When handling seed, augers or conveyors should be running slow and at full capacity to reduce damage.
The decision to pack before planting, after planting, or following emergence should be based on soil conditions. Packing helps to firm the soil so that moisture can move up through capillary action, benefiting crop emergence and uniformity. Packing creates a very fine, powdery surface that could easily seal and crust with rain. It is usually less harmful to roll before planting and then plant into the smooth surface, so the zone directly above the seed is not over-packed. Rolling a soybean field following emergence is an option for pushing in stones, leveling a field for direct harvest, or preparing a field for no-tilling a following crop. Roll only when the soybeans have fully emerged and not at the hook stage. Rolling during the heat of the day, when plants are flaccid, will reduce injury.
If a soybean inoculant is being used, check the product label for the “shelf life” when applied to the seed. Seed treatments can reduce the length of time that inoculant rhizobia remain viable on the seed. Some inoculants now include an extender which increases the length of time that rhizobia remain viable on the seed. Ontario data now suggests that using an inoculant in fields with a history of soybeans can increase soybean yields by
1 bu/ac.
The mild winter and cool, wet weather has been favourable for soil insects. Chafers, June beetles, seedcorn maggot, and slugs could pose a risk in some soybean fields. Fields at risk of having chafer are sandy soils, fields recently rotated out of sod, or those with a history of weeds, corn, cereals and other grasses. Fields at risk of having seedcorn maggot are those with recently applied surface manure or incorporated green material (any decaying vegetation that would attract an adult fly to lay its eggs). Cruiser seed treatment works very well on soybeans for chafer and June beetle grubs, and on seedcorn maggot.
Canola
Planting of spring canola is 50-70% complete in southern areas, with northern areas just starting. Recent rainfall brought relief to the cold and dry soil conditions that has delayed emergence. To assess the condition of seed which has not emerged, check that the emerging hypocotyl (shoot) is firm and white in colour. If the seed runs out of moisture during emergence, the hypocotly will dry out, turn brown and wilt. This can be confused with damping off caused by seedling disease, which is more likely if conditions are cool and wet for extended periods.
Flea beetles will soon begin emerging from overwintering sites. At temperatures of 15–20ºC, flea beetles become much more active taking flight in search of food. Populations can explode under warm, calm, sunny weather. Seed treatments provide 2 - 4 weeks of control under light to moderate flea beetle pressure. Canola stands should be monitored during the 3-4 weeks following emergence. For information on scouting and control, refer to OMAFRA Publication 811, Agronomy Guide and Publication 812, Field Crop Protection Guide.
Winter Cereals
With the return to seasonal temperatures, the wheat crop has jumped ahead. Tremendous variability in stand development exists, mainly due to planting date. Growth stages range from Zadok’s 25 to 32. The bulk of the crop is at Stage 31 (first node), which is the beginning of stem elongation. Corn Row Syndrome is showing in some wheat fields. This is an indication that wheat yields would have benefited from an increased rate of seed applied phosphorus at planting.
Several areas suffered frost damage between April 28th and 30th. Counties that were hit the worst were Lambton and Middlesex. Damage to the wheat crop was significantly worse in fields that were sprayed for weed control 1 to 3 days prior to the frost. With the growing point still alive, even the worst hit field will bounce back from the frost injury. In some of the coldest areas, under seeded red clover, beyond the cotyledon growth stage was killed by frost.
Weed control is wrapping up. After cereals reach growth Zadok Stage 31 (first node), increased damage occurs from wheel traffic, herbicide tolerance of the crop begins to decline, and the impact from weed competition has already occurred.
Septoria and mildew are beginning at very low levels, but overall disease levels remain extremely low, and below thresholds for control. Fungicide information is available in Field Crop Protection Guide, OMAFRA Publication 812 www.omafra.gov.on.ca/english/crops/pub812/p812toc.html.
Spring Cereals
Planting is nearing completion with 95% of the crop in the ground. Early seeded fields are showing excellent emergence and early growth. If planting is delayed beyond May 10th, consider switching to another crop. Cereal yields decline by 1.5 bu/ac/day when planted after May 10th. If spring cereals are required for the straw, shift to 6-row barley varieties because they tolerate heat stress and late planting better than other cereal types.
Scout fields for weeds. Broadleaf weeds have emerged with the cereal crop and should be sprayed between Zadok’s Growth Stage 12 and 15 of the cereals (3 to 5 leaf stages). Because of the advanced stage of weed development, timing of weed control and disease control will usually differ enough that tank mixing of the herbicide and fungicide will not be feasible. No-till fields with heavy dandelion pressure should be sprayed with dichlorprop/2,4-D for best control (do not use on oats). Refer to OMAFRA Publication 75 “Guide to Weed Control” to determine the product of choice for good weed control. Consult product labels for weeds controlled and application timing (www.omafra.gov.on.ca/english/crops/pub75/pub75toc.htm).